#出错原因：Ruby版本较低 需要升级 或者未安装Ruby版本
1.移除现有的Ruby
终端输入：gem sources --remove https://rubygems.org/
2.使用淘宝镜像
终端输入：gem sources -a https://ruby.taobao.org/
3.验证当前ruby版本
终端输入：gem sources -l
成功后提示：
*** CURRENT SOURCES ***
https://ruby.taobao.org/
4.开始安装cocoapods
终端输入：sudo gem install cocoa pods
这时候提示：
Fetching: i18n-0.7.0.gem (100%)
Successfully installed i18n-0.7.0
Fetching: thread_safe-0.3.5.gem (100%)
Successfully installed thread_safe-0.3.5
Fetching: tzinfo-1.2.2.gem (100%)
Successfully installed tzinfo-1.2.2
Fetching: minitest-5.9.0.gem (100%)
Successfully installed minitest-5.9.0
Fetching: concurrent-ruby-1.0.2.gem (100%)
Successfully installed concurrent-ruby-1.0.2
Fetching: activesupport-5.0.0.gem (100%)
ERROR: Error installing cocoapods:
activesupport requires Ruby version >= 2.2.2.
这个地方很坑，之前安装cocoapods一直是没有这个问题的，这里提示Ruby版本要大于或等于2.2.2
于是查看ruby版本
终端输入：ruby -v
ruby 2.0.0p648 (2015-12-16 revision 53162) [universal.x86_64-darwin15]
果然这里就要升级Ruby版本啦
查看目前的所有ruby版本：
终端输入：rvm list known
如果提示command not found 请先安装rvm
终端输入：curl -L get.rvm.io | bash -s stable
如果已安装会列出所有的ruby版本：
# MRI Rubies
[ruby-]1.8.6[-p420]
[ruby-]1.8.7[-head] # security released on head
[ruby-]1.9.1[-p431]
[ruby-]1.9.2[-p330]
[ruby-]1.9.3[-p551]
[ruby-]2.0.0[-p648]
[ruby-]2.1[.8]
[ruby-]2.2[.4]
[ruby-]2.3[.0]
[ruby-]2.2-head
ruby-head
# for forks use: rvm install ruby-head- --url https://github.com/github/ruby.git --branch 2.2
# JRuby
jruby-1.6[.8]
jruby-1.7[.23]
jruby[-9.0.5.0]
jruby-head
# Rubinius
rbx-1[.4.3]
rbx-2.3[.0]
rbx-2.4[.1]
rbx[-2.5.8]
rbx-head
# Opal
opal
# Minimalistic ruby implementation - ISO 30170:2012
mruby[-head]
# Ruby Enterprise Edition
ree-1.8.6
ree[-1.8.7][-2012.02]
# GoRuby
goruby
# Topaz
topaz
# MagLev
maglev[-head]
maglev-1.0.0
# Mac OS X Snow Leopard Or Newer
macruby-0.10
macruby-0.11
macruby[-0.12]
macruby-nightly
macruby-head
# IronRuby
ironruby[-1.1.3]
ironruby-head
这里我们安装2.2.2:
终端输入：rvm install 2.2.2
终端运行结果：（如果直接成功请绕过homebrew的卸载安装）
Searching for binary rubies, this might take some time.
Found remote file https://rvm_io.global.ssl.fastly.net/binaries/osx/10.11/x86_64/ruby-2.2.2.tar.bz2
Checking requirements for osx.
About to install Homebrew, press `Enter` for default installation in `/usr/local`,
type new path if you wish custom Homebrew installation (the path needs to be writable for user)
:
回车：(注意：一定要回车)
It appears Homebrew is already installed. If your intent is to reinstall you
should do the following before running this installer again:
ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"
The current contents of /usr/local are .git
Requirements installation failed with status: 1.
这里执行：
终端输入：ruby -e "$(curl -fsSL
https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"
卸载home-brew
Warning: This script will remove:
/Library/Caches/Homebrew/
/usr/local/.git/
Are you sure you want to uninstall Homebrew? [y/N] y
==> Removing Homebrew installation...
==> Removing empty directories...
==> Homebrew uninstalled!
You may want to restore /usr/local's original permissions
sudo chmod 0755 /usr/local
sudo chgrp wheel /usr/local
再执行：
终端输入：rvm install 2.2.2
提示：
Searching for binary rubies, this might take some time.
Found remote file https://rvm_io.global.ssl.fastly.net/binaries/osx/10.11/x86_64/ruby-2.2.2.tar.bz2
Checking requirements for osx.
About to install Homebrew, press `Enter` for default installation in `/usr/local`,
type new path if you wish custom Homebrew installation (the path needs to be writable for user)
:
按回车：(注意：一定要回车)
==> This script will install:
/usr/local/bin/brew
/usr/local/Library/...
/usr/local/share/doc/homebrew
/usr/local/share/man/man1/brew.1
/usr/local/share/zsh/site-functions/_brew
/usr/local/etc/bash_completion.d/brew
Press RETURN to continue or any other key to abort
==> /usr/bin/sudo /bin/mkdir /Library/Caches/Homebrew
Password: （终端输入密码）
这里需要输入电脑密码：
==> /usr/bin/sudo /bin/chmod g+rwx /Library/Caches/Homebrew
==> /usr/bin/sudo /usr/sbin/chown haha /Library/Caches/Homebrew
==> Downloading and installing Homebrew...
remote: Counting objects: 501, done.
remote: Compressing objects: 100% (445/445), done.
remote: Total 501 (delta 29), reused 360 (delta 27), pack-reused 0
Receiving objects: 100% (501/501), 787.83 KiB | 169.00 KiB/s, done.
Resolving deltas: 100% (29/29), done.
From https://github.com/Homebrew/brew
* [new branch] master -> origin/master
HEAD is now at 32f7e73 download_strategy: ensure fixed commit hash length
==> Tapping homebrew/core
Cloning into '/usr/local/Library/Taps/homebrew/homebrew-core'...
remote: Counting objects: 3714, done.
remote: Compressing objects: 100% (3598/3598), done.
remote: Total 3714 (delta 14), reused 2112 (delta 6), pack-reused 0
Receiving objects: 100% (3714/3714), 2.88 MiB | 240.00 KiB/s, done.
Resolving deltas: 100% (14/14), done.
Checking connectivity... done.
Checking out files: 100% (3717/3717), done.
Tapped 3591 formulae (3,740 files, 9.0M)
==> Installation successful!
==> Next steps
Run `brew help` to get started
Further documentation: https://git.io/brew-docs
==> Homebrew has enabled anonymous aggregate user behaviour analytics
Read the analytics documentation (and how to opt-out) here:
https://git.io/brew-analytics
Installing requirements for osx.
Updating system.....
Installing required packages: autoconf, automake, libtool, pkg-config, libyaml, readline, libksba, openssl........
Certificates in '/usr/local/etc/openssl/cert.pem' are already up to date.
Requirements installation successful.
ruby-2.2.2 - #configure
ruby-2.2.2 - #download
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 6854k 100 6854k 0 0 61342 0 0:01:54 0:01:54 --:--:-- 132k
ruby-2.2.2 - #validate archive
ruby-2.2.2 - #extract
ruby-2.2.2 - #validate binary
ruby-2.2.2 - #setup
ruby-2.2.2 - #gemset created /Users/haha/.rvm/gems/ruby-2.2.2@global
ruby-2.2.2 - #importing gemset /Users/haha/.rvm/gemsets/global.gems..............................
ruby-2.2.2 - #generating global wrappers........
ruby-2.2.2 - #gemset created /Users/haha/.rvm/gems/ruby-2.2.2
ruby-2.2.2 - #importing gemsetfile /Users/haha/.rvm/gemsets/default.gems evaluated to empty gem list
ruby-2.2.2 - #generating default wrappers........
Updating certificates in '/etc/openssl/cert.pem'.
mkdir: /etc/openssl: Permission denied
mkdir -p "/etc/openssl" failed, retrying with sudo
haha password required for 'mkdir -p /etc/openssl':
and sudo mkdir worked
这样ruby2.2.2就安装好了
现在就可以安装cocoapods啦：
终端输入：sudo gem install cocoa pods
看看这样cocoapods就安装成功了
Fetching: nap-1.1.0.gem (100%)
Successfully installed nap-1.1.0
Fetching: fourflusher-0.3.2.gem (100%)
Successfully installed fourflusher-0.3.2
Fetching: escape-0.0.4.gem (100%)
Successfully installed escape-0.0.4
Fetching: colored-1.2.gem (100%)
Successfully installed colored-1.2
Fetching: concurrent-ruby-1.0.2.gem (100%)
Successfully installed concurrent-ruby-1.0.2
Fetching: thread_safe-0.3.5.gem (100%)
Successfully installed thread_safe-0.3.5
Fetching: tzinfo-1.2.2.gem (100%)
Successfully installed tzinfo-1.2.2
Fetching: i18n-0.7.0.gem (100%)
Successfully installed i18n-0.7.0
Fetching: activesupport-5.0.0.gem (100%)
Successfully installed activesupport-5.0.0
Fetching: claide-1.0.0.gem (100%)
Successfully installed claide-1.0.0
Fetching: xcodeproj-1.1.0.gem (100%)
Successfully installed xcodeproj-1.1.0
Fetching: molinillo-0.4.5.gem (100%)
Successfully installed molinillo-0.4.5
Fetching: cocoapods-try-1.0.0.gem (100%)
Successfully installed cocoapods-try-1.0.0
Fetching: netrc-0.7.8.gem (100%)
Successfully installed netrc-0.7.8
Fetching: cocoapods-trunk-1.0.0.gem (100%)
Successfully installed cocoapods-trunk-1.0.0
Fetching: cocoapods-stats-1.0.0.gem (100%)
Successfully installed cocoapods-stats-1.0.0
Fetching: cocoapods-search-1.0.0.gem (100%)
Successfully installed cocoapods-search-1.0.0
Fetching: cocoapods-plugins-1.0.0.gem (100%)
Successfully installed cocoapods-plugins-1.0.0
Fetching: cocoapods-downloader-1.0.1.gem (100%)
Successfully installed cocoapods-downloader-1.0.1
Fetching: cocoapods-deintegrate-1.0.0.gem (100%)
Successfully installed cocoapods-deintegrate-1.0.0
Fetching: fuzzy_match-2.0.4.gem (100%)
Successfully installed fuzzy_match-2.0.4
Fetching: cocoapods-core-1.0.1.gem (100%)
Successfully installed cocoapods-core-1.0.1
Fetching: cocoapods-1.0.1.gem (100%)
Successfully installed cocoapods-1.0.1
Parsing documentation for nap-1.1.0
Installing ri documentation for nap-1.1.0
Parsing documentation for fourflusher-0.3.2
Installing ri documentation for fourflusher-0.3.2
Parsing documentation for escape-0.0.4
Installing ri documentation for escape-0.0.4
Parsing documentation for colored-1.2
Installing ri documentation for colored-1.2
Parsing documentation for concurrent-ruby-1.0.2
Installing ri documentation for concurrent-ruby-1.0.2
Parsing documentation for thread_safe-0.3.5
Installing ri documentation for thread_safe-0.3.5
Parsing documentation for tzinfo-1.2.2
Installing ri documentation for tzinfo-1.2.2
Parsing documentation for i18n-0.7.0
Installing ri documentation for i18n-0.7.0
Parsing documentation for activesupport-5.0.0
Installing ri documentation for activesupport-5.0.0
Parsing documentation for claide-1.0.0
Installing ri documentation for claide-1.0.0
Parsing documentation for xcodeproj-1.1.0
Installing ri documentation for xcodeproj-1.1.0
Parsing documentation for molinillo-0.4.5
Installing ri documentation for molinillo-0.4.5
Parsing documentation for cocoapods-try-1.0.0
Installing ri documentation for cocoapods-try-1.0.0
Parsing documentation for netrc-0.7.8
Installing ri documentation for netrc-0.7.8
Parsing documentation for cocoapods-trunk-1.0.0
Installing ri documentation for cocoapods-trunk-1.0.0
Parsing documentation for cocoapods-stats-1.0.0
Installing ri documentation for cocoapods-stats-1.0.0
Parsing documentation for cocoapods-search-1.0.0
Installing ri documentation for cocoapods-search-1.0.0
Parsing documentation for cocoapods-plugins-1.0.0
Installing ri documentation for cocoapods-plugins-1.0.0
Parsing documentation for cocoapods-downloader-1.0.1
Installing ri documentation for cocoapods-downloader-1.0.1
Parsing documentation for cocoapods-deintegrate-1.0.0
Installing ri documentation for cocoapods-deintegrate-1.0.0
Parsing documentation for fuzzy_match-2.0.4
Installing ri documentation for fuzzy_match-2.0.4
Parsing documentation for cocoapods-core-1.0.1
Installing ri documentation for cocoapods-core-1.0.1
Parsing documentation for cocoapods-1.0.1
Installing ri documentation for cocoapods-1.0.1
Done installing documentation for nap, fourflusher, escape, colored, concurrent-ruby, thread_safe, tzinfo, i18n, activesupport, claide, xcodeproj, molinillo, cocoapods-try, netrc, cocoapods-trunk, cocoapods-stats, cocoapods-search, cocoapods-plugins, cocoapods-downloader, cocoapods-deintegrate, fuzzy_match, cocoapods-core, cocoapods after 146 seconds
23 gems installed